Background: Encephalitis as the result of human herpesvirus (HHV)-6 is usually fatal when it is resistant to antiviral drugs.
Methods: We describe a patient who developed HHV-6 encephalitis after human leukocyte antigen-haploidentical transplantation using a reduced intensity regimen.
Results: The patient developed severe disorientation, amnesia, and tremors on day 28. Magnetic resonance imaging of the brain revealed limbic encephalitis, and the cerebrospinal fluid sample was positive for only HHV-6 in polymerase chain reaction analysis. Neither ganciclovir nor foscarnet was effective. The patient recovered from the critical condition of HHV-6 encephalitis after donor lymphocyte infusion (DLI). Almost all of his symptoms resolved, polymerase chain reaction tests for HHV-6 in the cerebrospinal fluid were negative, and magnetic resonance imaging findings were normal.
Conclusions: This is the first report of DLI as a treatment for HHV-6 encephalitis and the first report of DLI from an human leukocyte antigen-haploidentical donor as a treatment for life-threatening viral infection.